1. Field of the Invention
Embodiments of the invention relate generally to a security inspection system, and in particular to an inspection system that provides physical isolation by mechanically, electromagneticly, and radiologically isolating sensor technologies, from each other, and the outside world to produce a system with a unique and novel performance capability.
2. Discussion of the Related Art
A number of different inspection and detection systems have been developed for screening items such as passenger baggage, checked baggage, packages, cargo, vehicles and the like. These items may be screened for explosives, weapons, drugs, contraband, threat objects, and other items of interest. Conventional inspection systems operate using a variety of different technologies including nuclear quadrupolar resonance (NQR), X-ray computed tomography (CT), nuclear magnetic resonance (NMR), and magnetic resonance imaging (MRI), among others. Regardless of which technology the inspection system utilizes, the system typically contains some type of sensor system. High performance is achieved when each sensor is effectively isolated from other areas of the system, and the outside world. This isolation is necessary to optimize the inspection process to provide a high probability of detection and a low probability of false alarm, and to protect the outside environment from potentially harmful effects such as electromagnetic interference and ionizing radiation.
For example, in a typical NQR inspection system, a conveyor transports baggage into an inspection chamber defined by a radio frequency (RF) coil. Once positioned within the RF coil, the baggage is typically irradiated with pulses or sequences of pulses of electromagnetic radiation. For proper operation, a conventional NQR inspection system requires a structure, or active subsystem, in order to provide the necessary electromagnetic interference/radio frequency interference (EMI/RF) shielding from external noise. A tunnel, commonly known as a “wave guide below cut-off,” is often utilized to provide the necessary RFI shielding. In general, the length of the tunnel is about the same as the maximum cross-sectional dimension of the inspection chamber.
Inspection systems employing conveyers often utilize two such tunnels. One tunnel is located at the entrance to the inspection chamber, and a second tunnel is located at the exit. The length of each tunnel of a typical passenger baggage inspection system may range from about 24-48 inches, or more. The two shielding tunnels can double the overall size of the inspection system. In many applications, the size of the inspection system is not particularly important. However, there has been recent interest in utilizing increased numbers of inspection systems within existing environments such as airports and seaports. In such environments, space is limited and an inspection system having reduced overall size is highly desirable.